What is autism?
Autism refers to a wide range of neurodevelopmental disorders. Generally speaking, autism spectrum disorders (ASD) represent developmental impairment caused by differences in the brain. People with this disorder often have problems with social communication and interaction and limited or repetitive behavior or interests. They can also have different ways of learning, moving, or maintaining attention.
There are five main types of autism, which include Asperger's syndrome, Rhett syndrome, childhood disintegrative disorder, Kanner's syndrome, and general developmental disorder.
Due to the increasing number of cases of people with autistic disorders, scientists are trying to find the causes and predisposing factors of these health disorders, as well as opportunities for inclusion and normal lifestyle. Meanwhile, a new study explores the role of food as a suspected culprit in developing autism, specifically processed foods.
The study by the University of Central Florida team
A new study from the University of Central Florida, published in Scientific Reports on June 19, 2019, puts forward arguments for the emerging link between autism and the human microbiome. High levels of propionic acid (PPA), which is used in processed foods to extend shelf life and inhibit mold growth, appear to reduce the development of neurons in the fetal brain. [ref. 1]
Analyzing the role of nutrition in better understanding autism is nothing new. This study actually looked at the mother's diet in the onset of autism in the developing fetus. Such a finding, if proven to be true, could have important implications for advancing prenatal care and autism prevention.
Highlights of the study
As the team wrote, compiled by Latifa S. Abdelli, Aseela Samsam and Saleh A. Naser, autism spectrum disorder (ASD) is characterized by neuroinflammation and gastrointestinal symptoms. The spectrum includes different levels of impaired social communication, as well as repetitive behaviors that impede progress in learning and the child's ability to connect with others. [ref. 2]
The number of children diagnosed with autistic disorders is increasing every year. Obviously, there are things that are changing in societies that are causing this leap. In 2000, the CDC observed one in every 150 children exhibiting such behavior. By 2018, that number climbed to one in 59.
The research team notes that thousands of genes are linked to autism spectrum disorders. Although there is no single likely culprit, they believe it is an interaction between genetic and environmental factors, and in the study they focused on abnormalities of the mother's immune system. One of the scientists, who specializes in gastroenterological research, has turned to PPA because he had previously observed high levels of this carboxylic acid in stool samples of children with autism. In the intestines of children with autism there appear to be an increased number of Clostridia spp., Bacteriodetes and Desulfovibrio spp. known to be active digesters and producers of SCFA (short-chain fatty acids), including PPA and BA (butyrate).
Excessive levels of propionic acid reduce the number of neurons in the brain while overproducing glial cells, leading to inflammation, which is a marker of autism. Increased amounts of PPA damage the neural pathways that allow the brain to communicate with the body. This toxic cocktail responds to the symptoms of autism: repetitive behaviors, mobility problems, problems communicating with others.
Because PPA induces glial cell differentiation and an increase in TNF-α and IL-10 transcription and translation, the scientists suggest that PPA exposure during pregnancy may be associated with gliosis and inflammation, as reported in multiple neurodevelopmental diseases, including ASD. Specifically, exposure to high-dose PPA during the early stages of neural stem cell development promotes glial cell proliferation and activation, recapitulating the state of neuroinflammation as reported in the postpartum period in the brains of children with autism.
However, it is important to mention that propionic acid naturally occurs in the human microbiome. However, the increased amounts of acid consumed by mothers through processed foods have a negative effect on their children. The increased amount of PPA passes into the fetus, potentially stopping the development of neurons, which can help trigger the cascading effects that lead to the spectrum.
The acid was first discovered in 1844 by the Austrian chemist Johann Gottlieb, who noticed it in digested sugar products. Isolated, it causes an unpleasant body odor. Produced, however, the acid is used to stop mold in animal feed as well as in human food, including grains, baked goods and cheese. It is approved for use in the EU, USA, Australia and New Zealand.
In EU legislation we find the so-called. Commission Implementing Regulation (EU) No 1222/2013 of 29 November 2013 concerning the authorisation of propionic acid, sodium propionate and ammonium propionate as feed additives for ruminants, pigs and poultry [Ref. 3] It states: 'Substances listed in the Annex belonging to the category 'technological additives' and the functional group 'silage additives' as additives in animal nutrition are authorised under the conditions laid down in that Annex.' One of these substances is propionic acid.
Previous research has linked too high levels of PPA to nasal and throat irritation, birth defects and cancer (in rats). The new study suggests that the effects of PPA on the mother's microbiome are much greater than previously thought. According to the researchers, this is only a first step, but important for better understanding autism spectrum disorders and providing a better life for people with autism spectrum disorders.
